The realization of output-increasing or efficiency-increasing conversions on hot-gas generators, such as a gas turbine plant for example, generally entails changes in the parameters of the hot gas. Such “upgrades”, but also fuel changes, etc., typically lead to a change in the parameters of the hot gas. This is significant for the downstream constructions, in particular in the case of a downstream technological process for the material and/or thermal utilization of the hot gas, for example in the case of a heat-recovery boiler for utilizing the waste heat.
The thermal process of, for example, a heat-recovery boiler depends to a great extent on the gas-side temperature conditions and flow conditions. Adaptation of the heat-recovery boiler to the changed conditions is very difficult. In addition, the design conditions may be exceeded at an increased gas temperature.
In order not to influence the technological processes downstream of a gas turbine plant in the event of an upgrade, attempts are made by means of suitable measures to keep the parameters of the gas constant, or to limit them, in accordance with the design conditions of the heat-recovery boiler.
In principle, the gas-side temperatures and also mass flows can be increased or reduced individually or in combination by conversion measures on gas turbine plants.
The output of a gas turbine plant essentially depends on the mass flow, and the efficiency essentially depends on the process temperature. For the aforesaid reasons, it is attempted to increase these parameters individually or in combination, which entails higher mass flows and temperatures of the hot gas.
In the prior art, by way of example for gas turbine plants, measures for adapting the parameters of the hot gas have been proposed for the situation of both too high a gas temperature and too low a gas temperature.
Thus, for example, DE 198 45 763 A1 describes measures for the situation of too high a gas temperature. To lower the temperature of the exhaust gases, a coolant (in the specific case air or steam) is admixed with the exhaust gases between gas turbine and exhaust-gas system. Attempts to cool the exhaust gases by means of water injection are also known. In addition, in this connection, a special air-inlet passage is described in DE 199 61 540 A1.
For the opposite situation of too low a gas temperature, in particular auxiliary combustion systems are proposed. To increase the temperature of the exhaust gases, auxiliary combustion systems, for the most diverse reasons, are known in the most diverse embodiments with and without blowers. The blowers serve in this case, inter alia, to increase the gas mass flow, for example in order to ensure a sufficient oxygen feed or to guarantee an operation at part load or during stoppage of the gas turbine plant. In this connection, for example, the following applications maybe cited: EP 1 050 667 A1; DE 101 09 336 A1; DE 199 61 540 A1; DE 43 19 936 A1; EP 0 967 366 A1; DE 197 34 862 A1.